The present invention relates to thermal protection and more particularly to reusable protection members which can be used on objects subject to great heating, such as aircraft or spacecraft.
When a spacecraft returning from a random orbit enters the atmosphere, it is subject to very great kinetic heating due to the deceleration exerted on it by the atmosphere. The heating period is dependent on the reentry trajectory and lasts about 15 to 25 minutes. The kinetic flows or fluxes are very considerable at the nose of the craft and on the leading edges of the wings and fins, high on the wing lower surface and on the sides of the aircraft and less high on the wing upper surface, which is still exposed to significant local heating. It is therefore vital to protect the craft to prevent deterioration of the airframe and equipment and even the loss of the craft, because the temperature reached can exceed 1000.degree. C. and even 2000.degree. to 2500.degree. C. at certain places. The effectiveness of the protection must vary from one area to another as a function of the particular thermal flux. The same problems are encountered with a very fast craft which does not leave the atmosphere.
The main method used at present consists of covering the craft with tiles, each of which constitutes an isolated protection member. These tiles must adapt to the curvature of their support and to the cutouts at the location of connections, doors, hatches, etc. Therefore their geometry, varies between individual tiles in three dimensions. Moreover, depending on the location on the craft where they are located, the efficiency required as a function of the thermal flux differs. Thus, the insulation title thicknesses differ and thickness may not be constant for a given tile.
This clearly leads to a certain number of disadvantages due to the fact that the tiles are almost all different. This makes it necessary to have a high number of title specifications, a high production cost rate due to the variety of tools required, a high development and qualification cost due to the numerous installation configurations, and high inspection and control costs because the equipment for the same must be adapted to each tile and numerous qualification tests are required. Finally, the inspections title required between two flights are very long and complicated.
Another method consists of producing rigid and e.g., parallelepipedic members, associating on the one hand one or more refractory shields and on the other an insulating layer. The refractory shield or shields are located on the outside and are therefore exposed to the aerodynamic flow, whilst the insulating layer is between the refractory shield and the craft structure. Optionally, the refractory shields can be wavy in order to aid the compensation of thermal expansions.
This system has the same disadvantages as that based on tiles described hereinbefore, because each rigid member must be designed so that it is adapted to the local thermal and geometrical conditions of the area which it has to cover.